Power transmission assembly

Abstract

A pedal powered gear transmission mechanism applicable to velocipedes, exercise machines or winches is disclosed. A system of non-circular gears or a combination of non-circular and circular gears between pedal cranks and a chain driving sprocket causes the pedal cranks to retard and advance cyclically relative to the chain sprocket by varying the instantaneous gear ratio between the pedal cranks and chain sprocket. The resulting change in mechanical advantage partially compensates for the inherent disadvantage at and near dead center pedal positions. A more uniform application of torque is developed.

I claim: 
     
       1. In a power transmission assembly, cranking means, a support for the cranking means, gearing including at least a pair of meshing non-circular gears and further including a gear secured to the cranking means to turn therewith and forming the power input gear for said gearing, support and enclosing means for said gearing, a shaft on said support and enclosing means, a power output gear formed from one of said non-circular gears, and being rotatively mounted on said craning means, a gear rotatably mounted on said shaft in meshing relationship with said power input gear and being rigidly connected to the other of said pair of non-circular gears, and chain drive means fixed to the power output gear, said pair of meshing non-circular gears being elliptical gears which are ninety degrees out of phase with each other. 
     
     
       2. In a power transmission assembly as defined in claim 1, said gearing including two meshing pairs of elliptical gears with the gears in each pair being ninety degrees out of phase with each other. 
     
     
       3. In a power transmission assembly as defined in claim 2, and said cranking means comprising pedal operated crank arms, a rotary spindle connected with and turned by said crank arms, and one gear of said gearing being secured to said rotary spindle. 
     
     
       4. In a power transmission assembly as defined in claim 3, and said support comprising a vehicular frame, and said support and enclosing means being a housing for said gearing. 
     
     
       5. In a power transmission assembly as defined in claim 4, and said support and enclosing means having a torque reactive connection with said support. 
     
     
       6. In a power transmission assembly as defined in claim 5, and said vehicular frame having a hub within which said rotary spindle is journaled, said housing including a part engaging the exterior of said hub, and a fastener element interconnecting said part and said hub and forming said torque reactive connection. 
     
     
       7. In a power transmission assembly as defined in claim 6, and said vehicular frame comprising a bicycle frame, and said chain drive means fixed to said power output gear including at least a single chain driving sprocket. 
     
     
       8. A power transmission assembly, comprising, a housing for said assembly, a spindle on said housing, a first elliptical gear on said spindle, a shaft on said housing in parallel relationship to said spindle, a second elliptical gear rotatively mounted on said shaft in meshing relationship with said first gear, a third elliptical gear rigidly joined to said second gear for rotatively movement about said shaft, and a fourth elliptical gear rotably mounted on said spindle in meshing relationship to said third gear, power input means connected to said spindle, power output means connected to said fourth gear and wherein said gears are ninety degrees out of phase with the gear to which they are in meshing relationship.